# NTSB DEN84FA004: Cessna 421C, N770JW, Center, CO, October 9, 1983

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Field investigation · Final report
- Date: October 9, 1983, 10:20 local (16:20 UTC)
- Place: Center, CO
- Coordinates: 37.750415, -106.110382 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.7504&lon=-106.1104&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 3 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 16173
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN84FA004
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/16173/pdf
- Page: https://openairdocs.org/ntsb/DEN84FA004

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of engine power(partial) - mech failure/malf, takeoff - roll/run
  - exhaust system,turbocharger - overspeed (contributing factor)
  - maintenance,inspection - inadequate, other maintenance personnel (cause)
  - operation with known deficiencies in equipment - attempted, pilot in command (contributing factor)
  - throttle/power control - improper use of, pilot in command (cause)
- Loss of control - on ground/water, takeoff - roll/run
  - directional control - not maintained, pilot in command (cause)
  - aborted takeoff - delayed, pilot in command (cause)
  - ground loop/swerve - performed, pilot in command (cause)
- On ground/water encounter with terrain/water, takeoff - roll/run
  - terrain condition - dirt bank/rising embankment (contributing factor)
- Gear collapsed, takeoff - roll/run

## Analysis

THE ACFT COLLIDED WITH A DIRT BANK AFTER A LEFT ENGINE OVERSPEED AND LOSS OF DIRECTIONAL CONTROL DURING TAKEOFF. THE PLTHAD ALREADY ABORTED ONE TAKEOFF DUE TO OVERBOOST AND A STICKING WASTEGATE. THE PROBLEM SEEMED CORRECTED AFTER WORK AND LUBRICATION BY A MECHANIC AND WORKED SATISFACTORILY FOR ABOUT A MONTH. THEN DURING THIS TKOF THE OVERBOOST WAS ENOUGH TOCAUSE THE PLT TO LOSE DIRECTIONAL CONTROL AND DEPART THE RWY. THE PLT WAS TRYING TO 'SAVE THE TAKEOFF' BY RETURNING TO THE RWY WHEN THE ACFT WING STRUCK A DIRT PILE. POST ACCIDENT INVESTIGATION SHOWED THAT A STICKING VALVE IN THE TURBOCHARGER WASTEGATE OF THE LEFT ENGINE AND A STUCK PRESSURE RELIEF VALVE CAUSED THE OVERBOOST CONDITION.

## Aircraft

- Registration: [N770JW](https://openairdocs.org/deregistered/N770JW-2013-06-07), registration cancelled 2013-06-07, S/N 421C-1052, built 1981 (OpenAirDocs)
- Reported make and model: CESSNA 421C
- Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs)
- Registry engine: [Continental GTSIO-520-C](https://openairdocs.org/engine/continental-gtsio-520-c) (registry code 17035, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 1052
- Airframe hours: 877
- Engines: CONTINENTAL GTSIO-520-N 375 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Registered owner: Jerry Spearman
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, September 22, 1983, 26 hours before
- Destination: DTN, SHREVEPORT, LA
- Flight plan: IFR
- Airport: IV8, Leach, runway 30, 7,100 × 48 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 51; commercial; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 6,330 total, 74 in this make and model, 5,350 as pilot in command, 49 in the last 90 days, 9 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 100 statute miles
- Lowest ceiling: none
- Temperature: 75 °F

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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